TUESDAY, April 9 (HealthDay News) -- The shingles vaccine is effective but few American seniors get it, according to a new study.

Shingles is a painful skin and nerve infection that occurs when the chickenpox virus is reactivated in older adults who had chickenpox as children. The vaccine helps prevent reactivation of the virus.

Researchers led by Sinead Langan from the London School of Hygiene and Tropical Medicine examined data collected from more than 766,000 Medicare beneficiaries between 2007 and 2009, and found that the vaccine reduced the rate of shingles by 48 percent overall.

However, the vaccine was less effective in seniors with weakened immune systems, according to the report published April 9 in the journal PLoS Medicine.

The vaccine reduced the rate of a painful shingles-related complication called post-herpetic neuralgia by 59 percent, the investigators found.

Despite its effectiveness, less than 4 percent of the seniors in the study had received the vaccine. Rates of vaccination were particularly low among blacks (0.3 percent) and people with low incomes (0.6 percent), according to a journal news release.

"The findings are relevant beyond U.S. medical practice, being of major importance to the many countries, including the U.K., that are actively considering introducing the [shingles] vaccine into routine practice in the near future," Langan and colleagues concluded.